U.S. patent application number 14/522330 was filed with the patent office on 2015-04-30 for image reading apparatus and image forming apparatus.
The applicant listed for this patent is CANON FINETECH INC.. Invention is credited to Nobuyuki Tochigi.
Application Number | 20150116791 14/522330 |
Document ID | / |
Family ID | 52995106 |
Filed Date | 2015-04-30 |
United States Patent
Application |
20150116791 |
Kind Code |
A1 |
Tochigi; Nobuyuki |
April 30, 2015 |
IMAGE READING APPARATUS AND IMAGE FORMING APPARATUS
Abstract
An image reading apparatus sets an irradiation region below a
fixed reading glass when light guide members diffuse light of LEDs
upward so that the irradiation region corresponding to a
significantly sagged portion in a main scanning direction is wider
than that corresponding to portions on both sides of the
significantly sagged portion, and sets a light intensity of a
plurality of LEDs corresponding to the significantly sagged portion
in the main scanning direction to be larger than that of a
plurality of LEDs corresponding to the portions on both sides of
the significantly sagged portion. Therefore, the degradation of the
illuminance corresponding to the significantly sagged portion due
to the pressed fixed reading glass can be prevented, and the entire
document can be read with uniform reading precision.
Inventors: |
Tochigi; Nobuyuki;
(Kawaguchi-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON FINETECH INC. |
Misato-shi |
|
JP |
|
|
Family ID: |
52995106 |
Appl. No.: |
14/522330 |
Filed: |
October 23, 2014 |
Current U.S.
Class: |
358/475 |
Current CPC
Class: |
H04N 2201/0081 20130101;
H04N 1/40056 20130101; H04N 2201/0094 20130101; H04N 1/0281
20130101; H04N 1/02885 20130101; H04N 1/1039 20130101 |
Class at
Publication: |
358/475 |
International
Class: |
H04N 1/10 20060101
H04N001/10; H04N 1/40 20060101 H04N001/40; H04N 1/028 20060101
H04N001/028 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 2013 |
JP |
2013-224675 |
Claims
1. An image reading apparatus, comprising: a transparent member on
which a document is placed; and a light source configured to emit
light for irradiating the document placed on the transparent
member, the light source emitting the light so that a light
intensity irradiated on a second portion of the transparent member,
which has a larger deflection amount than that of a first portion
of the transparent member, is larger than a light intensity
irradiated on the first portion in a deflecting direction of the
second portion.
2. An image reading apparatus according to claim 1, wherein the
deflecting direction of the second portion corresponds to a
downward direction.
3. An image reading apparatus according to claim 1, wherein a
portion of the transparent member, which has a largest deflection
amount when the document is placed on the transparent member,
corresponds to a central portion of the transparent member.
4. An image reading apparatus according to claim 1, further
comprising: a moving member arranged below the transparent member
and configured to reciprocate in a sub-scanning direction; the
light source including a plurality of light sources provided in the
moving member; and a light guide member provided in the moving
member so as to be spaced away from and opposed to a lower surface
of the transparent member, and configured to guide the light of
each of the plurality of light sources to a region below the
transparent member in a main scanning direction, and to diffuse the
light upward so as to irradiate the document placed on the
transparent member, wherein, when the light guide member diffuses
the light of the each of the plurality of light sources upward, a
diffusion region below the transparent member includes a wide
region and a narrow region in the main scanning direction, and
wherein a light intensity of the each of the plurality of light
sources in the main scanning direction is set so that the light
intensity corresponding to the wide region is larger than the light
intensity corresponding to the narrow region in the main scanning
direction.
5. An image reading apparatus according to claim 4, wherein an
arrangement pitch of the plurality of light sources corresponding
to the wide region is set to be narrower than an arrangement pitch
of the plurality of light sources corresponding to the narrow
region.
6. An image reading apparatus according to claim 4, wherein an
emission intensity of the each of the plurality of light sources
corresponding to the wide region is set to be larger than an
emission intensity of the each of the plurality of light sources
corresponding to the narrow region.
7. An image reading apparatus according to claim 4, further
comprising a diffusion sheet provided on a light exit surface of
the light guide member corresponding to the wide region.
8. An image reading apparatus according to claim 4, wherein a light
exit surface of the light guide member corresponding to the wide
region is formed as a roughened surface for diffusing the light of
the each of the plurality of light sources.
9. An image reading apparatus according to claim 4, wherein the
wide region corresponds to a central portion in the main scanning
direction of the light guide member, and wherein the narrow region
corresponds to portions on both sides of the central portion.
10. An image reading apparatus according to claim 9, wherein the
light intensity of the each of the plurality of light sources
corresponding to the central portion in the main scanning direction
is set to be larger than the light intensity of the each of the
plurality of light sources corresponding to the portions on both
the sides of the central portion, and to be smaller than the light
intensity of the each of the plurality of light sources
corresponding to portions on an outer side of the portions on both
the sides.
11. An image forming apparatus, comprising: the image reading
apparatus according to claim 4, which is configured to read an
image of the document; and an image forming unit forming an image
on a sheet based on image reading information read by the image
reading apparatus.
12. An image reading apparatus, comprising: a transparent member on
which a document is placed; a moving member arranged below the
transparent member and configured to reciprocate in a sub-scanning
direction; a plurality of light sources provided in the moving
member and configured to emit light for irradiating the document
placed on the transparent member; a light guide member provided in
the moving member so as to be spaced away from and opposed to a
lower surface of the transparent member, and configured to guide
the light of each of the plurality of light sources to a region
below the transparent member in a main scanning direction, and to
diffuse the light upward so as to irradiate the document placed on
the transparent member; a deflection amount detection unit
detecting a downward deflection amount of the transparent member;
and an emission intensity adjustment unit configured to adjust an
emission intensity of the each of the plurality of light sources
based on an electric current, wherein the emission intensity
adjustment unit increases the emission intensity of the each of the
plurality of light sources corresponding to a portion having a
large deflection amount in the main scanning direction as the
deflection amount detected by the deflection amount detection unit
is larger.
13. An image reading apparatus according to claim 12, wherein the
portion having a large deflection amount corresponds to a central
portion in the main scanning direction.
14. An image forming apparatus, comprising: the image reading
apparatus according to claim 12, which is configured to read an
image of the document; and an image forming unit forming an image
on a sheet based on image reading information read by the image
reading apparatus.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an image reading apparatus,
and an image forming apparatus having an apparatus body including
the image reading apparatus.
[0003] 2. Description of the Related Art
[0004] FIG. 8 is a schematic cross-sectional view taken along a
moving direction K1 of a carriage 807 of an image reading apparatus
800 according to a comparative example. Light L emitted from an LED
801 of the carriage 807 passes through a light guide member 802 and
illuminates a document surface (image surface) Gf of a document G
placed on a fixed reading glass 803. The carriage 807 reads a
two-dimensional image of the document surface Gf through line
reading in a main scanning direction orthogonal to the moving
direction K1 and movement in a sub-scanning direction that is the
moving direction K1. The light L reflected from the document
surface Gf is further reflected by a plurality of reflecting
mirrors 804, and forms an image on a photoelectric conversion
element 806 by an imaging optical unit 805. Then, the light L is
converted into an electrical signal.
[0005] In general, the light L emitted from the LED 801 has such a
light distribution characteristic that the light is bright at a
center and becomes darker in positions away from the center. A
light intensity obtained when only one LED 801 is used as a light
source to illuminate the document is not sufficient to illuminate
the document. Therefore, a plurality of LEDs 801 is necessary. A
portion including the LEDs 801 and the light guide member 802
serves as a document illumination unit 808.
[0006] There is such an image reading apparatus that, when the LEDs
801 in the document illumination unit 808 are used as a light
source for document illumination, the plurality of LEDs are
arranged in an array form to prevent degradation of a peripheral
light intensity due to the imaging optical unit 805 and this
arrangement has been devised (Japanese Patent Application Laid-Open
No. S61-142857).
[0007] In this image reading apparatus, a large number of light
emitting elements are arranged in a main scanning direction, and at
least one of an emission intensity of each light emitting element
and an arrangement pitch between the light emitting elements is
changed so that an intensity of irradiation light from both end
portions in the main scanning direction is larger than that from a
central portion in the main scanning direction. As a result, in the
image reading apparatus, a cosine-fourth-law characteristic of an
imaging lens is corrected in an illuminance distribution on a
document irradiation surface in advance.
[0008] In the image reading apparatus according to the comparative
example, there is a problem in that, when the fixed reading glass
803 serving as a transparent member is deflected in a direction
approaching the carriage 807, the illuminance is insufficient and
uneven, and the entire document cannot be read with uniform reading
precision.
[0009] As illustrated in FIG. 9, when a document GB having a great
thickness and a binding portion, such as papers or a book, is
placed on the fixed reading glass 803 by a user, there is a gap C
between the document GB and the fixed reading glass 803. In order
to reduce the gap C, the user strongly presses the document GB
against the fixed reading glass 803 through intermediation of a
pressing plate 847 for covering the fixed reading glass 803 (in a
direction indicated by an arrow W). Then, a pressed portion of the
fixed reading glass 803 may be elastically deformed downward from a
flat position indicated by a solid line and may be deflected as
indicated by a dashed line. When the fixed reading glass 803 is
deflected downward, the distance between the fixed reading glass
803 and the carriage 807 is not uniform. Therefore, in the image
reading apparatus according to the comparative example, there is a
problem in that the illuminance is insufficient and uneven, and the
entire document cannot be read with uniform reading precision.
[0010] Further, an image forming apparatus having an apparatus body
including such an image reading apparatus has a problem in that a
high-quality image cannot be formed.
SUMMARY OF THE INVENTION
[0011] The present invention provides an image reading apparatus
capable of suppressing degradation of illuminance near a
significantly sagged portion and unevenness of illuminance even
when a transparent member on which a document is placed is strongly
pressed and a portion of the transparent member in the main
scanning direction is significantly sagged, and also provides an
image forming apparatus including the image reading apparatus.
[0012] According to one embodiment of the present invention, there
is provided an image reading apparatus, including: a transparent
member on which a document is placed; and a light source configured
to emit light for irradiating the document placed on the
transparent member, the light source emitting the light so that a
light intensity irradiated on a second portion of the transparent
member, which has a larger deflection amount than that of a first
portion of the transparent member, is larger than a light intensity
irradiated on the first portion in a deflecting direction of the
second portion.
[0013] According to another embodiment of the present invention,
there is provided an image reading apparatus, including: a
transparent member on which a document is placed; a moving member
arranged below the transparent member and configured to reciprocate
in a sub-scanning direction; a plurality of light sources provided
in the moving member and configured to emit light for irradiating
the document placed on the transparent member; a light guide member
provided in the moving member so as to be spaced away from and
opposed to a lower surface of the transparent member, and
configured to guide the light of each of the plurality of light
sources to a region below the transparent member in a main scanning
direction, and to diffuse the light upward so as to irradiate the
document placed on the transparent member; a deflection amount
detection unit detecting a downward deflection amount of the
transparent member; and an emission intensity adjustment unit
configured to adjust an emission intensity of the each of the
plurality of light sources based on an electric current, wherein
the emission intensity adjustment unit increases the emission
intensity of the each of the plurality of light sources
corresponding to a portion having a large deflection amount in the
main scanning direction as the deflection amount detected by the
deflection amount detection unit is larger.
[0014] According to one embodiment of the present invention, there
is provided an image forming apparatus, including: any one of the
above-mentioned image reading apparatus configured to read an image
of the document; and an image forming unit forming an image on a
sheet based on image reading information read by the image reading
apparatus.
[0015] In the image reading apparatus of the present invention, the
light intensity of the region in which the diffusion region in the
main scanning direction is wide is set to be larger than that of
the narrow region, and hence it is possible to prevent the
degradation of the illuminance when the transparent member is
pressed and sagged, and to read the entire document with uniform
reading precision.
[0016] In the image reading apparatus of the present invention, the
emission intensity adjustment unit increases the emission light
intensity source corresponding to the portion having a large
deflection amount in the main scanning direction as the deflection
amount detected by the deflection amount detection unit is larger,
and hence it is possible to prevent the degradation of the
illuminance when the transparent member is pressed and sagged.
Further, it is possible to read the entire document with uniform
reading precision.
[0017] The image forming apparatus of the present invention
includes the image reading apparatus capable of reading the entire
document with uniform reading precision, and hence it is possible
to form a high-quality image on a sheet.
[0018] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a cross-sectional view taken along a sheet
conveying direction of an image forming apparatus according to a
first embodiment of the present invention.
[0020] FIG. 2 is a schematic cross-sectional view taken along a
moving direction (sub-scanning direction) of a carriage of an image
reading apparatus according to the first embodiment of the present
invention.
[0021] FIG. 3A is a plan view of a light source and a light guide
member illustrated in FIG. 2.
[0022] FIG. 3B shows a light intensity emitted from the light guide
member.
[0023] FIG. 4A is a cross-sectional view taken along a sub-scanning
direction of a fixed reading glass and a light guide member as
indicated by an arrow IVA-IVA of FIG. 3A.
[0024] FIG. 4B is a cross-sectional view taken along the
sub-scanning direction of the fixed reading glass and the light
guide member as indicated by an arrow IVB-IVB of FIG. 3A.
[0025] FIG. 5 illustrates a light guide member having a different
form from that of the light guide member of FIGS. 4A and 4B.
[0026] FIG. 6 is a schematic cross-sectional view taken along a
sub-scanning direction of an image reading apparatus according to a
second embodiment of the present invention.
[0027] FIG. 7 is a control block diagram of the image reading
apparatus according to the second embodiment of the present
invention.
[0028] FIG. 8 is a schematic cross-sectional view taken along a
sub-scanning direction of a carriage of an image reading apparatus
according to a comparative example.
[0029] FIG. 9 is a schematic view illustrating deformation of a
fixed reading glass of the image reading apparatus according to the
comparative example.
DESCRIPTION OF THE EMBODIMENTS
[0030] Now, an image reading apparatus according to embodiments of
the present invention and an image forming apparatus having an
apparatus body including the image reading apparatus are described
with reference to the drawings.
[0031] FIG. 1 is a cross-sectional view taken along a sheet
conveying direction of the image forming apparatus of the present
invention. Vertical and horizontal directions are indicated by
arrows in FIG. 1. Further, a direction intersecting the vertical
direction and the horizontal direction is a main scanning direction
(a direction indicated by an arrow K2 of FIG. 3A), and the
horizontal direction (a direction indicated by an arrow K1) is a
sub-scanning direction. Further, the sub-scanning direction K1 is a
moving direction of a carriage 50 to be described below.
[0032] An image forming apparatus 1 includes a box-shaped apparatus
body (body frame) 10, and an image reading apparatus 15 provided on
an upper part of the apparatus body 10. A sheet feed unit 11, an
image forming unit 12, a fixing unit 13, and a sheet delivery unit
14 are provided in this order from the bottom to the top in the
apparatus body 10 of the image forming apparatus. Further, a sheet
re-feed unit 16 is provided on the right side of the image forming
unit 12 and the fixing unit 13.
[0033] A sheet feed cassette 21, a pickup roller 22, a feed path
23, a feed roller pair 24, a registration roller pair 25, a manual
feed tray 26, and the like are arranged in the sheet feed unit 11.
Only one of sheets S received in a stacked state in the sheet feed
cassette 21 is separated due to rotation of the pickup roller 22
and fed to the feed path 23. Further, the sheet S is deflected by
coming in contact with a nip of the registration roller pair 25
stopping without rotation due to the feed roller pair 24, and skew
are straightened. The sheet S is also fed by a pickup roller 27 and
a feed roller pair 28 from the manual feed tray 26.
[0034] A photosensitive drum 31, and a charging roller 32, a laser
unit 33 serving as an exposure device, a developing roller 34, and
a transfer roller 35, which are arranged sequentially around the
photosensitive drum 31 in a rotation direction of the
photosensitive drum 31, are provided in the image forming unit
12.
[0035] A surface of the photosensitive drum 31 is uniformly charged
by the charging roller 32 and scanned with laser light from the
laser unit 33. Charge in a portion irradiated with laser light is
removed and an electrostatic latent image is formed on the surface
of the photosensitive drum 31. Toner is caused to adhere to the
electrostatic latent image by the developing roller 34 and
developed as a toner image. This toner image is conveyed to a
transfer nip portion N1 due to rotation of the photosensitive drum
31. In synchronization with this timing, the sheet S is fed from
the registration roller pair 25 to the transfer nip portion N1.
While the fed sheet S is nipped and conveyed in the transfer nip
portion N1, the toner image is transferred from the photosensitive
drum 31 onto the sheet S by the transfer roller 35. The laser light
radiated from the laser unit 33 is controlled ON and OFF based on
image reading information of a document surface (image surface) Gf
of a document G read by the image reading apparatus 15 to be
described below.
[0036] A fixing roller 41, a pressure roller 42, and the like are
arranged in the fixing unit 13. The fixing roller 41 is heated to a
predetermined fixing temperature (e.g., about 180.degree. C.) and
the pressure roller 42 is brought into contact with the fixing
roller 41 to form a fixing nip portion N2 between the rollers. The
sheet S having the toner image transferred onto the front surface
is conveyed into the fixing nip portion N2 and heated by the fixing
roller 41 while being nipped and conveyed in the fixing nip portion
N2. In this manner, the toner image is fixed onto the front
surface.
[0037] A delivery path 43, a delivery roller pair 44, a delivery
tray 45, and the like are arranged in the sheet delivery unit 14.
The sheet S having the fixed toner image is conveyed along the
delivery path 43 and delivered onto the delivery tray 45 by the
delivery roller pair 44.
[0038] The sheet re-feed unit 16 includes a re-feed path 48 and
re-feed roller pairs 49. When the toner image is to be also formed
on a back surface of the sheet S, the sheet S having the toner
image fixed onto the front surface is fed to the re-feed path 48 by
stopping the delivery roller pair 44 and rotating the delivery
roller pair 44 in a reverse direction before a trailing edge of the
sheet S is passed through the delivery roller pair 44. This sheet S
is conveyed along the re-feed path 48 by the re-feed roller pairs
49, enters the feed path 23, and is stopped by the registration
roller pair 25 stopping without rotation. The sheet S is then
delivered onto the delivery tray 45 after the toner image is
transferred and fixed onto the back surface, as in the case in
which the toner image is transferred and fixed onto the front
surface.
Image Reading Apparatus of First Embodiment
[0039] The image reading apparatus 15 includes a document feed unit
81 and an image reading unit 82. The document feed unit 81 is
provided on the image reading unit 82 in an openable and closable
manner.
[0040] The document feed unit 81 automatically conveys the document
G to the image reading unit 82. The document feed unit 81 conveys
the document G placed in a document tray 83 by a user to a
conveyance roller pair 85 using a pickup roller 84. The conveyance
roller pair 85 conveys the document G to a registration roller pair
86. The skewed document is straightened using the registration
roller pair 86 and the conveyance roller pair 85. Then, the
document G is fed onto a flow reading glass 89, on which the
document is read in a flowing manner, by a conveyance roller pair
87 and a white roller 88. The carriage 50 stopped under the flow
reading glass 89, which is described below, reads an image of the
document. The document from which the image has been read is
scooped from the flow reading glass 89 by a scooping member 90 and
delivered onto a delivery tray 92 by a delivery roller pair 91.
When both surfaces of the document are to be read, the document is
reversed by a reverse path 93 and conveyed to the flow reading
glass 89 again, and the image of the other surface is read by the
carriage 50. Finally, the document is delivered onto the delivery
tray 92. Thus, a method of causing the document to pass along the
flow reading glass and reading the document under a state in which
the carriage 50 is stopped in a position illustrated in FIG. 1 is
called flow reading.
[0041] The image reading unit 82 includes the carriage 50, a fixed
reading glass 46, the flow reading glass 89, and a moving device
52.
[0042] The moving device 52 includes, a motor 53, a driving pulley
54 fixed to an output shaft of the motor, a driven pulley 55, and a
wire 56 connected to the carriage across the pulleys, and moves the
carriage 50 in the sub-scanning direction K1. The moving device 52
rotates the motor 53 in a forward direction or a reverse direction
to rotate the driving pulley 54 in a forward direction or a reverse
direction and reciprocate the carriage 50 in the sub-scanning
direction K1 through intermediation of the wire 56. A document
illumination unit 70 to be described below is incorporated in the
carriage 50.
[0043] FIG. 2 is a cross-sectional view taken along the moving
direction (sub-scanning direction) of the carriage of the image
reading apparatus. The image reading unit 82 reads the document G,
which is placed on an upper surface of the fixed reading glass 46
with the document surface Gf being directed downward, as the
carriage 50 moves in the sub-scanning direction K1 below the fixed
reading glass 46. In this case, the document G is pressed against
the fixed reading glass 46 by the document feed unit 81, and the
document surface Gf is read.
[0044] The carriage 50 is moved in the sub-scanning direction K1 by
the moving device 52 (FIG. 1) while irradiating the document
surface Gf of the document G with light in the main scanning
direction K2 (FIG. 3A), to thereby scan the entire document surface
Gf and read image information. Thus, a method of moving the
carriage 50 in the sub-scanning direction K1 and reading the
document placed on the fixed reading glass 46 is called fixed
reading.
[0045] The image information is transmitted to the above-mentioned
laser unit 33 and used for ON-OFF control of the laser light. The
carriage 50 is further described below.
[0046] Next, the carriage 50 and the document illumination unit 70
of the image reading apparatus 15 are described with reference to
FIG. 2.
[0047] The carriage 50 includes a housing 61, the document
illumination unit 70, support members 62 and 63, a plurality of
mirrors 64, an imaging optical unit 65, and a photoelectric
conversion element 66 such as a CCD. The housing 61 is a moving
member having a box shape, and is arranged so as to reciprocate in
the sub-scanning direction K1 below the fixed reading glass
(transparent member) 46 and the flow reading glass 89 (FIG. 1) on
which the document G is located. The support members 62 and 63 are
members for mounting the document illumination unit 70 to the
housing 61 of the carriage. The photoelectric conversion element 66
is a long member extending along the main scanning direction (the
direction indicated by an arrow K2 of FIG. 3A), and is an
image-pickup element for receiving light reflected from the
document G to read the image information.
[0048] Inclined portions of a top surface of the housing 61 of the
carriage are illumination mounting portions 61a and 61b. The
document illumination unit 70 is mounted on the illumination
mounting portions 61a and 61b by the support members 62 and 63. A
slit Y is formed in a position on the housing 61 corresponding to
an axis La of reading light. The slit Y is formed along the main
scanning direction. The document illumination unit 70 is described
below.
[0049] The plurality of mirrors 64 are provided so as to increase
the number of times of reflection of light that has passed through
the slit Y and increase a length of an optical path of the light up
to the photoelectric conversion element 66. The imaging optical
unit 65 forms an image on the photoelectric conversion element 66
using the light reflected by the last mirror 64. The housing 61 of
the carriage reciprocates in the sub-scanning direction K1 through
guiding of a guide member (not shown) and driving of the moving
device 52 (FIG. 1).
[0050] Next, the document illumination unit 70 is described with
reference to FIGS. 3A and 3B. FIG. 3A is a plan view of the
document illumination unit 70 illustrated in FIG. 2. The document
illumination unit 70 includes a first light source array 71a, a
second light source array 71b, a first light guide member 72a, and
a second light guide member 72b. The first light guide member 72a
and the second light guide member 72b are long members, and are
provided in the housing 61 of the carriage in a direction
orthogonal to the moving direction K1 of the carriage 50. The
direction in which the first light guide member 72a and the second
light guide member 72b are arranged is the main scanning direction
K2. Further, the first light guide member 72a and the second light
guide member 72b are provided in the housing 61 of the carriage so
as to be spaced away from and opposed to lower surfaces of the flow
reading glass 89 and the fixed reading glass 46.
[0051] The first light source array 71a is arranged adjacent to the
first light guide member 72a in the main scanning direction K2. An
exit surface 73a is formed in the first light guide member 72a.
Light emitted from the first light source array 71a passes through
the first light guide member 72a, exits from the exit surface 73a
of the first light guide member 72a, and irradiates the document
G.
[0052] The second light source array 71b is arranged adjacent to
the second light guide member 72b in the main scanning direction
K2. An exit surface 73b is also formed in the second light guide
member 72b. Light emitted from the second light source array 71b
passes through the second light guide member 72b, exits from the
exit surface 73b of the second light guide member 72b, and
irradiates the document G.
[0053] The first light source array 71a, the second light source
array 71b, the first light guide member 72a, and the second light
guide member 72b serve as an illuminance degradation reduction
unit.
[0054] Shapes of the exit surface 73a of the first light guide
member 72a and the exit surface 73b of the second light guide
member 72b differ in central portions 73aa and 73ba in the main
scanning direction K2, portions (intermediate portions) 73ab and
73bb on both sides of the central portions, and end portions 73ac
and 73bc.
[0055] Further, the first light source array 71a and the second
light source array 71b include a plurality of LEDs 75a and 75b
arranged as light sources in the main scanning direction K2. The
LEDs 75a and 75b corresponding to the central portions, the
intermediate portions, and the end portions in the main scanning
direction K2 of the first light guide member 72a and the second
light guide member 72b have different arrangement pitches.
[0056] Here, the arrangement pitch of the LED 75a corresponding to
the central portion 73aa of the first light guide member 72a and
the LED 75b corresponding to the central portion 73ba of the second
light guide member 72b is assumed to be Pa. The arrangement pitch
corresponding to the portions (intermediate portions) 73ab and 73bb
on both sides of the central portions is assumed to be Pb. Further,
the arrangement pitch corresponding to the end portions 73ac and
73bc is assumed to be Pc.
[0057] Then, the following relationship is set.
Pb>Pa>Pc Expression 1
[0058] That is, a narrow arrangement pitch is set in the central
portions, a wide arrangement pitch, which is wider than that in the
central portions, is set in the intermediate portions, and a
narrower arrangement pitch, which is narrower than that in the
central portions, is set in the end portions.
[0059] The respective arrangement pitches may be equal within the
respective portions. However, in this case, a light intensity
exiting from the first and second light guide members suddenly
changes at boundaries between the respective portions. Therefore,
in order to prevent the light intensity from suddenly changing at
the boundaries between the respective portions, the pitches within
the respective portions may be unequal. That is, it is preferred to
have such an arrangement pitch that the light intensity exiting
from the first and second light guide members changes in a curved
manner, as shown in FIG. 3B.
[0060] Next, a document irradiation operation of the document
illumination unit 70 is described with reference to FIGS. 4A and
4B. FIGS. 4A and 4B are cross-sectional views taken along the
sub-scanning direction of the fixed reading glass and the light
guide member. FIG. 4A is a cross-sectional view taken along an
arrow IVA-IVA of FIG. 3A, and FIG. 4B is a cross-sectional view
taken along an arrow IVB-IVB of FIG. 3A.
[0061] In FIG. 4A, when a document (not shown) such as a book is
placed by a user and a pressing force W is applied via the document
feed unit 81 (FIG. 1), the fixed reading glass 46 may be deflected
downward as indicated by a dashed line from a position indicated by
a solid line. An arrow conceptually indicates a direction of the
light for irradiating the document. Further, a line La in FIG. 4A
indicates an axis of reading light of the document in the
sub-scanning direction.
[0062] The conventional light guide member was formed without
consideration for deflection of the fixed reading glass 46. A light
guide member has a condensing effect for a related-art tubular
light source. Therefore, when the fixed reading glass 46 is
deflected and a reading position is lowered, light exiting from the
light guide member having a uniform cross-section in the
sub-scanning direction is less likely to reach the vicinity of the
central portion in the main scanning direction, thus causing
degradation of illuminance.
[0063] However, in the first light guide member 72a and the second
light guide member 72b of this embodiment, shapes of the
cross-section in the sub-scanning direction differ in the central
portions 73aa and 73ba, the intermediate portions 73ab and 73bb,
and the end portions 73ac and 73bc in the main scanning
direction.
[0064] Reflecting surfaces 74aa and 74ba of the central portions
73aa and 73ba illustrated in FIG. 4A have smaller angles than the
reflecting surfaces 74ac and 74bc of the end portions 73ac and 73bc
illustrated in FIG. 4B. Angles (not shown) of the reflecting
surfaces 74ab and 74bb of the intermediate portions 73ab and 73bb
are medium angles between those in FIGS. 4A and 4B.
[0065] Therefore, partial light L1 exiting from the exit surfaces
73aa and 73ba of the central portions is refracted, and partial
light L2 is not refracted. As a result, when the first light guide
member and the second light guide member diffuse the light of the
LED upward, an irradiation region (diffusion region) AR below the
fixed reading glass 46 is set to be larger in the central portions
in the main scanning direction than in the portions (intermediate
portions) on both sides of the central portions and in the end
portions. Therefore, the irradiation region AR is widened downward
near the line La, and thus the reading position can be irradiated
with light even in the fixed reading glass 46 that has been
deflected as indicated by the dashed line.
[0066] When the shape of the light guide member is changed so as to
simply widen the irradiation region AR downward, a light intensity
per unit area decreases and the illuminance of the document
decreases. However, the arrangement pitch of the LEDs in the
central portion, in which the irradiation region is widened, is
narrower than that in the intermediate portion, as illustrated in
FIG. 3A or represented by Expression 1. Therefore, the light
intensity per unit area does not decrease even when the irradiation
region is widened. Accordingly, in the image reading apparatus 15,
it is possible to prevent degradation of the illuminance for the
document and maintain the image reading precision substantially
uniformly even when the fixed reading glass 46 is deflected
downward.
[0067] When the imaging optical unit 65 moves together with the
carriage, it is necessary for the imaging optical unit 65 to have a
wider angle than a 2:1 mirror scanning type imaging optical unit so
as to downsize the carriage.
[0068] When the imaging optical unit 65 has the wider angle, a
light intensity at peripheral angles of view decreases in
proportion to a cosine fourth power of a half angle of view of the
imaging optical unit 65. Therefore, the peripheral light intensity
decreases, for example, to 56% at the half angle of view of
30.degree. in comparison with the central portion.
[0069] When a light source array is arranged in the central portion
with the same arrangement pitch as the arrangement pitch of the
light source array at which light intensity degradation is reduced,
it is necessary to greatly increase an irradiation region of the
central portion and it is necessary for the shape of the light
guide member to greatly differ from the shape in the end portion.
Therefore, difficulty or cost of manufacture may increase. Further,
the greatly increased irradiation region may be highly likely to
cause stray light.
[0070] There are various arrangement pitches depending on the angle
of view of the imaging optical unit 65, but the arrangement pitch
satisfying the relationship of Expression 1 is preferred when the
imaging optical unit 65 moves together with the carriage as in this
embodiment.
[0071] In the document illumination unit 70 described above, the
cross-sectional shapes in the sub-scanning direction of the central
portions, the intermediate portions, and the end portions in the
main scanning direction of the first light guide member 72a and the
second light guide member 72b are changed so that the irradiation
region AR differs in the vertical direction. However, diffusion
sheets 176a and 176b may be provided on exit surfaces 173a and 173b
of central portions in the main scanning direction of a first light
guide member 172a and a second light guide member 172b illustrated
in FIG. 5 to enlarge the irradiation region AR in the vertical
direction. Alternatively, the exit surfaces 173a and 173b may be
formed as finely roughened surfaces (not shown), for example,
through sandblasting to enlarge the irradiation region AR in the
vertical direction. Thus, when the diffusion sheets are provided on
the exit surfaces 173a and 173b or when the exit surfaces 173a and
173b are formed as roughened surfaces, the same cross-sectional
shape in the sub-scanning direction may be employed over an entire
length of the first light guide member 172a and the second light
guide member 172b so that the shapes of the light guide members can
be simplified. In FIG. 5, reflecting surfaces 174a and 174b are
similar to the reflecting surfaces 74aa and 74ba of FIG. 4A.
[0072] The image reading apparatus 15 described above presses the
document against the fixed reading glass 46 using the document feed
unit 81, but the pressing plate 847 illustrated in FIG. 9 may be
provided in place of the document feed unit 81 and the document may
be pressed by the pressing plate 847. In this case, the flow
reading glass 89 is unnecessary.
[0073] In the above description, a light intensity for irradiating
the document through the first light guide members 72a and 172a and
the second light guide members 72b and 172b may be changed with the
same light intensities of the respective LEDs and different
arrangement pitches. However, the present invention is not limited
thereto and the light intensity for irradiating the document may be
changed with the same arrangement pitches and different light
intensities of the LEDs.
Image Reading Apparatus of Second Embodiment
[0074] Next, an image reading apparatus 215 according to a second
embodiment of the present invention is described with reference to
FIG. 6. The image reading apparatus 215 according to the second
embodiment includes a document feed unit 81 and an image reading
unit 282 similarly to the image reading apparatus 15 according to
the first embodiment. The document feed unit according to the
second embodiment has the same configuration as the document feed
unit according to the first embodiment, and the image reading unit
has a partially different configuration. Therefore, different
portions are mainly illustrated and described, and the same
portions are denoted with the same reference symbols to omit
repeated description.
[0075] A first light guide member 272a and a second light guide
member 272b of a carriage 250 are long members having the
cross-sectional shapes as illustrated in FIG. 4B over their entire
lengths in a main scanning direction. LEDs 275a and 275b are
arranged as light sources at equal intervals along outer end
portions in the main scanning direction of the light guide members
272a and 272b.
[0076] A document G placed on an upper surface of a fixed reading
glass 46 with a document surface Gf being directed downward is
pressed by a user through intermediation of the document feed unit
81, and is brought into close contact with the fixed reading glass
46 while the fixed reading glass 46 is deflected downward as
illustrated in FIG. 6. In this case, a scooping member 90 provided
between the fixed reading glass 46 and a flow reading glass 89 is
also deflected downward. The scooping member 90 is a long member
along the main scanning direction, and hence its central portion in
the main scanning direction is most deflected.
[0077] A reflecting member 257 is bonded onto a lower surface of
the central portion in the main scanning direction of the scooping
member 90. A distance measuring sensor 258 for detecting a
deflection amount when the fixed reading glass 46 and the scooping
member 90 are deflected downward is arranged under the reflecting
member 257. The distance measuring sensor 258 detects a downward
deflection amount of the fixed reading glass 46 by receiving
irradiation light reflected by the reflecting member 257. The
deflection amount is detected when the fixed reading glass 46 is
deflected downward and the reflecting member 257 approaches the
distance measuring sensor 258 so that distance therebetween is
shortened.
[0078] When the reflecting member 257 is provided within a reading
region of the fixed reading glass 46, light of the LEDs 275a and
275b is reflected and read by the image reading unit 282.
Therefore, the reflecting member 257 is provided on the lower
surface of the scooping member 90, which is arranged outside the
image reading region of the image reading unit 282 and deflected
similarly to the fixed reading glass 46. A shading white plate (not
shown) may be used as the reflecting member in place of a dedicated
reflecting member. In this case, the distance measuring sensor 258
needs to be provided under the shading white plate.
[0079] The distance measuring sensor 258 performs distance
measurement under a state in which the document has not yet been
placed on the fixed reading glass 46 when power is supplied to the
image forming apparatus 1, to thereby acquire an initial value of a
glass deflection amount. This initial value is stored in a ROM 259a
of a CPU 259 illustrated in FIG. 7. The initial value may be
acquired at the time of factory shipment and stored in the ROM 259a
in advance.
[0080] Then, the document G is set on the fixed reading glass 46
and the fixed reading glass 46 is closed with the document feed
unit 81. When the fixed reading glass 46 is closed and a copy start
button is pressed, the distance measuring sensor 258 performs the
distance measurement to acquire a current state value. Further, the
CPU 259 compares the initial value with the current state value
using a calculation unit 259b to calculate the deflection amount of
the fixed reading glass 46. As the deflection amount of the fixed
reading glass 46 increases, light deviates from the irradiation
region (diffusion region) AR of the first light guide member 272a
and the second light guide member 272b, and an irradiation
intensity of the LEDs 275a and 275b decreases. Therefore, as the
calculated deflection amount increases, the CPU 259 serving as an
emission intensity adjustment unit increases an electric current
value of the LEDs 275a and 275b corresponding to the central
portion in the main scanning direction to increase the light
intensity and compensate for the lack of the irradiation intensity
for the document. As a result, the image reading apparatus 215 can
maintain a substantially uniform light intensity for irradiating
the document even when the fixed reading glass 46 is deflected
downward, to thereby maintain uniform reading precision for the
document.
[0081] When the deflection amount of the fixed reading glass 46 is
large and the carriage 250 may interfere with the fixed reading
glass 46 due to its movement in the sub-scanning direction, the CPU
259 stops the carriage 250 without changing the electric current
and causes an operation panel 260 to display an abnormal state. The
operation panel 260 (FIG. 1) is provided in the apparatus body 10
of the image reading apparatus and is used for the user to input
information necessary for image formation, and to display an
operation status of the image forming apparatus. In the
above-mentioned configuration, the reflecting member 257 and the
distance measuring sensor 258 serve as a deflection amount
detection unit.
[0082] The image reading apparatus 215 described above presses the
document against the fixed reading glass 46 using the document feed
unit 81, but the pressing plate 847 illustrated in FIG. 9 may be
provided in place of the document feed unit 81 and the document may
be pressed by the pressing plate 847. In this case, the flow
reading glass 89 is unnecessary.
[0083] Further, the case in which the central portion in the main
scanning direction of the fixed reading glass 46 is deflected has
been described above, but the central portion in the main scanning
direction is not necessarily deflected depending on the structure
of the image reading apparatus. Therefore, a place in which the
fixed reading glass 46 is most deflected is not limited to the
central portion in the main scanning direction, and a region in
which the diffusion region of the light guide member is wide is not
limited to the central portion in the main scanning direction.
[0084] The exemplary embodiments of the present invention have been
described above, but the present invention is not limited to these
embodiments, and various modifications and alterations may be made
within the scope of the gist of the present invention. For example,
it is preferred that portions other than an incident portion of the
light guide member have various shapes depending on
specifications.
[0085] Further, the image forming apparatus including the
above-mentioned image reading apparatus can copy a high-quality
image on the sheet.
[0086] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0087] This application claims the benefit of Japanese Patent
Application No. 2013-224675, filed Oct. 29, 2013, which is hereby
incorporated by reference herein in its entirety.
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